As an oil pump configured as mentioned above, Patent Document 1 discloses a configuration that has a drive gear (exemplary rotor) that is rotationally driven by an engine and an internal tooth driven gear (exemplary tubular body) that meshes with the drive gear, and is provided with a single suction port, two discharge ports, and an oil pressure control valve that controls the flow of oil from the two discharge ports.
In Patent Document 1, the oil pressure control valve is provided with a valve body that controls the flow of hydraulic oil from one of the discharge ports, and a spring that causes a biasing force to act on the valve body. With this oil pump, when the engine rotational speed is low, hydraulic oil from the two discharge ports is merged and pumped out. Then, when the rotational speed of the engine increases, excess supply of hydraulic oil is suppressed by returning some of the hydraulic oil from one of the discharge ports to the suction port using the valve body, and merging the remainder with the hydraulic oil from the other discharge port.
In Patent Document 1, oil can thus be supplied with the required characteristics by combining an oil pressure control valve with an internal gear pump having two discharge ports.
Patent Document 2 shows an internal gear pump in which an inner rotor that has outer teeth and is driven around a drive rotation axis and an outer rotor (exemplary tubular body) that has inner teeth that mesh with the inner rotor (exemplary rotor) in an eccentric state and rotates around the rotation center are provided inside a casing. An adjustment ring is provided that causes the rotation center of the outer rotor to revolve about the drive rotation axis in a state where the inner rotor meshes with the outer rotor, and the pump capacity can be changed by causing the outer rotor to revolve with operation of the adjustment ring.
In Patent Document 2, a coil spring is provided that biases the adjustment ring to a predetermined position, and an oil pressure hydraulic system that causes the adjustment ring to revolve against the biasing force of the coil spring, and the capacity of the oil pump can be changed by switching between a state of supplying hydraulic oil to the oil pressure hydraulic system via an electromagnetic valve and a state of allowing hydraulic oil to flow out.
Patent Documents 3 and 4 describe variable-capacity vane oil pumps in which the pump capacity is changed by oscillating a cam ring (exemplary tubular body).
The oil pump described in Patent Document 3 is provided with a first pressure chamber that applies an oscillating force to the cam ring such that the amount of eccentricity of the cam ring relative to the revolution axis of the rotor decreases, a second pressure chamber that applies an oscillating force to the cam ring such that the amount of eccentricity increases, and an electromagnetic valve that selectively supplies hydraulic fluid to the second pressure chamber.
The oil pump described in Patent Document 4 is provided with a first control chamber that causes a force that reduces the pump capacity to act on the cam ring, a second control chamber that causes a force that increases the pump capacity to act on the cam ring, and an electromagnetic valve that selectively supplies hydraulic fluid to the second control chamber.